Specific terminology is used to describe flowers and their
parts. Many flower parts are fused together; fused parts
originating from the same whorl are connate, while fused
parts originating from different whorls are adnate; parts
that are not fused are free. When petals are fused into a
tube or ring that falls away as a single unit, they are
sympetalous (also called gamopetalous). Connate petals
may have distinctive regions: the cylindrical base is the
tube, the expanding region is the throat and the flaring
outer region is the limb. A sympetalous flower, with
bilateral symmetry with an upper and lower lip, is bilabiate.
Flowers with connate petals or sepals may have various
shaped corolla or calyx, including campanulate, funnelform,
tubular, urceolate, salverform or rotate.
Referring to "fusion," as it is commonly done, appears
questionable because at least some of the processes
involved may be non-fusion processes. For example, the
addition of intercalary growth at or below the base of the
primordia of floral appendages such as sepals, petals,
stamens and carpels may lead to a common base that is
not the result of fusion
